The objective of this application is to investigate the feasibility of utilizing the characteristic prompt optical emissions generated during pulsed laser lithotripsy for automatic and rapid feedback control of the laser energy delivery system. The goal is to minimize the risk of injury resulting from inadvertent irradiation of healthy soft tissue. The concept proposed involves using the characteristic laser-induced optical signals promptly emitted by calculi to control a fast electro-optic beam shutter in the laser device. A simple electronic logic circuit interrogates the resulting optical emission early in the laser pulse. If the characteristic prompt optical emissions associated with calculi are not observed the electro-optic beam shutter is rapidly closed thereby preventing any significant discharge of energy from the delivery fiber. It is anticipated that his scheme will work well with any repetitively-pulsed laser delivering microsecond or longer pulses. If successful this research would lead to the development of a reliable, real-time automated beam control algorithm and associated hardware that would greatly reduce the risk of laser injury to healthy soft tissue during pulsed laser lithotripsy procedures (urinary and biliary). Such a control system would also have great potential for use in a number of pulsed laser angioplasty systems under development.